Assessment of worker exposure to a volatile organic chemical (VOC) requires measuring the airborne concentration of the vaporphase and the coexisting particle phase separately because the resulting inhalation dose can differ substantially. American Conference of Governmental Industrial Hygienists (ACGIH) has suggested establishing dual Threshold Limit Values (TLVs) for the two phases of a volatile substance. However, due to particle evaporation and vapor absorption by the particle surface in the sampling process, air samplers presently in use are not adequate for efficient separation of the VOC vapor and particles and currently there are no simple field sampling methods to measure the size distribution of particles that contain VOCs. The first goal of the proposed research is to develop a prototype Vapor/Particle Sampler (VPS) for anisokinetic separation of the airborne VOC containing particles and coexisting vapor into two identifiable fractions according to their differential inertia. Our second goal is to develop a prototype Multiple Vapor/Particle Sampler (MVPS) system, which not only can separate vapor and particles, but also can provide the size classification of the particles that contain VOCs. The aerodynamic cut-off sizes of the MVPS system will be designed to 1, 2, 3.5, 5, 10 and 20 micromole aerodynamic diameter. Where, 3.5 and 10 micromole are the ACGIH defined particle cut sizes for respirable and thoracic particulate mass fractions, respectively. The proposed VPS sampler and the MVPS particle size analyzing system will be appropriate for monitoring the airborne concentrations of VOCs in the industrial spray work environment, such as the reinforced plastic industry and the paint spray booth. They are relatively simple and inexpensive field sampling devices and will provide essential data for the assessment of worker exposure to the vapor and particle phases of a VOC and important reference data for establishing dual Threshold Limit Values (TLVs) for both phases.